Enter the frequency offset in hertz and select the reference frequency into the calculator to determine the equivalent parts per million, or use the formula below to convert Hz to ppm manually.
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Hz to PPM Formula
The following formula is used to calculate the frequency error in parts per million from a frequency offset in hertz.
ppm = (Δf / fnominal) × 10^6
Variables:
- ppm is the frequency error in parts per million
- Δf is the frequency offset in hertz
- fnominal is the nominal or reference frequency in hertz
To calculate ppm, divide the frequency offset by the nominal frequency and multiply the result by 1,000,000.
If you need to convert ppm back into hertz, use the inverse relationship below.
Δf = (ppm × fnominal) / 10^6
What is Hz to PPM?
Converting Hz to ppm expresses a frequency error as a relative deviation instead of an absolute one. This is useful for oscillators, clocks, crystals, synthesizers, and measurement systems because the same error in hertz can represent a very different level of accuracy depending on the nominal frequency. For example, a 1 Hz error at 1 MHz equals 1 ppm, while a 1 Hz error at 10 MHz equals only 0.1 ppm.
Hz to PPM Conversion Table
The table below shows the ppm value for a 1 Hz offset at several common reference frequencies.
| Nominal Frequency | Frequency Offset (Δf) | Equivalent in PPM |
|---|---|---|
| 32.768 kHz | 1 Hz | 30.52 ppm |
| 1 MHz | 1 Hz | 1 ppm |
| 10 MHz | 1 Hz | 0.1 ppm |
| 100 MHz | 1 Hz | 0.01 ppm |
| 1 GHz | 1 Hz | 0.001 ppm |
How to Convert Hz to PPM?
The following steps outline how to convert a frequency offset in hertz into ppm.
- First, determine the frequency offset, Δf, in hertz.
- Next, determine the nominal or reference frequency, fnominal, in hertz.
- Divide the frequency offset by the nominal frequency.
- Multiply the result by 1,000,000 to calculate the error in ppm.
- After inserting the values and calculating the result, check your answer with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge.
Frequency Offset (Δf) = 1 Hz
Reference Frequency (fnominal) = 10 MHz
Hz to PPM = (1 / 10,000,000) × 1,000,000 = 0.1 ppm
This is why very small errors in hertz can still matter in high-precision timing and frequency applications.